Control system for electric translating devices



y 1941- w. J. KUTCHER 2.247.506

CONTROL SYSTEM FOR ELECTRIC 'I'RANSLATING DEVICES Filed Jan. 20, 1939 2Sheets-Sheet 1 L|--7 M L2? u 4 m: c L3 T 1 1 M 28% INVENTORS f 2 WILLIAMJ. KUTCHER &

JOHN D.LE|TCH THEIR ATTORNEY.

July 1, 1941. w. J. KUTCHER EIAL CONTROL SYSTEM FOR ELECTRIC TRANSLATINGDEVICES Filed Jan. 20, 1939 2 Sheets-Sheet 2 REV 432! m ATTORNEY.

Patented Jul 1, 1941 CONTROL SYSTEM FOR EIEOTBIC TRANS- LATING DEVICESWilliam J. Kutcher, East Cleveland, Ohio, and John D. Leitch, Manhalset,N. Y., asslgnorl to The Electric Controller & Manufacturing Company,Cleveland, Ohio. a corporation of Ohio Application January 20, 1939,Serial No. 252,060

18 Claims.

This invention relates to a control system for an electric translatingdevice, the illustrative example hereinafter disclosed being an improvedcontrol system for automatically short circuiting the starting impedancein a motor circuit during acceleration of the motor and introducing atime delay between the closing of successive starting switches, theextent of the time delay intervals being influenced by the load on themotor during acceleration. Embodiments of the invention in connectionwith other electric translating devices are apparent from theillustrative example and will not be specifically described.

Heretofore, in the control of translating devices by timing circuits,timing circuits similar to that hereinafter described have beenprovided, but the prior circuits have been operatively connected to thetranslating device in a manner such that the timing intervals thereofwere in indirect relation to the magnitude of that electrical conditionof the translating device on which the timing circuit depended for itsenergization. Such a timing circuit, so related, is set forth anddescribed in United States Letters Patent No. 2,024,019, issued onDecember 10, 1935, to David C. Wright. The timing circuit was employedin the Wright patent for a resistance welder and provided a timeinterval which was indirectly related to the magnitude of the currentflowing through the welding electrodes. The timing circuit employed inthe present invention, in many respects, is similar to that of theWright patent, but is connected differently to the translating device soas to provide timin intervals which are directly related to the amountof current flowing to an electric translating device, or, in theillustrative example, which are in direct relation to the load on themotor.

Various well known means have heretofore been used for automatically andsuccessively short circuiting portions of the starting resistance in amotor circuit so that the starting current of the motor would not exceedcertain predetermined values. Those systems which provide a definitetime delay between the successive closing of the resistance shuntingswitches have, among other disadvantages, the disadvantage that, if thetime delay periods are adjusted for an intermediate load, the periodsare too long for lighter loads and too short for heavier loads. As oneexample,

that often during cold weather the acceleration contactors close tooquickly if the acceleration time is definitely predetermined. As anotherexample, a motor may be used to drive a wide range of loads varying fromtwice full load to extremely light loads. If the acceleration time isset so that excessive current peaks are prevented from occurring underheavy loads, then, on light loads, the motor is accelerated at a muchlower rate than is economically or otherwise desirable.

In order to overcome such disadvantages in the case of direct currentmotors, systems have been developed for automatically excluding startingresistance at a rate dependent upon the electrical condition of a motorcircuit during the accelerating period. Two of the more common of suchsystems are known as counter electromotive force acceleration andcurrent limit acceleration. One of the disadvantages common to both ofthese systems is that they cannot start or accelerate a stalled or tooheavily loaded motor since, under such conditions, the counterelectromotive force either does not exist or does not increase. In thecase of current limit acceleration, the current does not decreasesufficiently to cause relay operation unless the motor rotates at anappreciable speed. Various means have been used to eliminate thesedefects, and such improved systems are known as combined time limit andcurrent limit. All of such improved systems, however, are primarilyadapted to determine only short time intervals, generally are notreadily adjustable for difierent load conditions, and are not adaptablefor use with alternating current motors.

Again, one or two minutes may be required to bring an alternatingcurrent or direct current motor driving a heavy inertia load up to fullspeed. This necessitates either the use of many acceleration steps, eachhaving a relatively short time interval, or the use of fewer steps, eachhaving a longer time interval. The use of fewer steps of longer durationis the more economical of the two, but heretofore has not been used toas great an extent as desired because of the difliculty of providing asatisfactory means to measure the long time intervals.

The present invention is an automatic motor control system which iscapable of causing acceleration at a rate dependent upon the motor loadduring the accelerating period, and capable of causing the startingresistance to be shunted even though the motor is stalled or the amountof motor current is excessive. The present system also is operative in-amanner such that the duration of time which may be Obtained between thesuccessive operations of the accelerating switches is practicallyunlimited and the time delay intervals may be readily adjusted over awide range, whereby the system is adaptable for use with motors drivingany type of load and with motors which inherently require a longacceleration period.

For purposes of illustration, the invention is disclosed in detail inthe drawings and description hereof as applied to alternating currentmotors, but the invention is not to be limited to the exemplaryembodiments.

The invention, in one illustrative embodiment, includes a. transformerwhich supplies alternating current to a rectifier, and the directcurrent output of the rectifier charges a condenser to a predeterminedvoltage. Upon the attainment of the predetermined voltage, the condenserdischarges through a discharge device and operating winding of a relaywhich is thereupon operated to control an accelerating contactor. Inorder to modify the charging time of the condenser in accordance withthe load on the motor, the primary of the transformer includes twowindings. One of these windings is a potential winding connected acrosstwo of the supply conductors leading to the motor, and the other is acurrent winding connected in series with one of the supply conductors.The flux set up by the current winding is opposed to that set up by thepotential winding so that the resulting flux, and consequently thesecondary voltage of the transformer, are reduced in accordance with theelectrical condition of the motor circuit, for example, in inverserelation to the amount of motor current. Since the charging time of thecondenser is inversely dependent upon the resulting flux, any reductionin the resulting flux increases the condenser charging time andconsequently provides a longer time interval before the relay operates.

Another illustrative embodiment of the invention is one which effectscontrol of alternating current motors wherein a separate currenttransformer is utilized instead of the current winding of the singletransformer. In such instance, the current transformer has its primarywinding in series with a conductor leading to the motor, and thesecondary voltage of the separate current transformer is rectified andthe direct current output from the rectifier is connected in oppositionto the rectified output from a potential transformer which is connectedacross the supply conductors. The reduced direct current voltageresulting from the opposition of the voltages charges a condenser to apredetermined potential, and necessarily the charging interval isgreater than would be required were the potential transformer voltage orcurrent transformer voltage used alone. Due to the opposed voltages,therefore, the time interval becomes directly related to the amount ofcurrent flowing in the primary winding of the current transformer. Thus,the condenser absorbs energy in an inverse relation to the motorcurrent, and, consequently, the heavier the load on the motor, thegreater the motor current, the less the condenser charging voltage, andthe longer the acceleration time.

An object of the present invention is to provide a system forcontrolling the operation of an electric translating device inaccordance with the differential between two similar, but relativelyvarying, electrical conditions of different circuits, one of which isassociated with the device and in one of which the said condition iscontinuously predominant over the said similar condition of the other.

One of the principal objects of the present invention is to provide asystem for controlling the operation of an electric translating deviceby an operative relation between a condenser and the current conditionof the device such that the charging rate of the condenser is inverselyrelated to the current condition of the device.

Another object is to provide a control system for an electric motor inwhich a means responsive to a predetermined potential is connectedacross an electric energy absorbing device so as to change the conditionof motor operation in inverse relation to the load on the motor.

An important object of the invention is to provide a system of motoracceleration for a motor in which a time delay device is provided whichmay be adjusted to provide a suitable acceleration of the motor undernormal working conditions and which, without change or adjustment,accelerates the motor properly under different or changing conditions orunder abnormal working conditions.

A correlative object of the present invention is to provide a system ofmotor control which combines all of the advantages of the definite timedelay systems and the current limit systems and which can be adjustedreadily to provide a wide range of acceleration periods.

Another object is to provide a motor control system incorporating asingle time delay device which controls a plurality of acceleratingswitches in response to variations in the value of current in a motorcircuit, the time delay intervals betwen operation of the switches beinglonger when the current value is large and being shorter when thecurrent value is small.

The long time intervals obtainable by this invention makes it especiallysuitable for the control of primary resistance or reactor type starters,and of reduced voltage starters for alternating current motors.Synchronous motors are generally brought up to speed as inductionmotors, and, as the speed approaches synchronism, full voltage isapplied to the armature winding and direct current is applied to thefield winding. Heretofore, it has been necessary to use a relay having adefinite time delay in order to obtain the long time interval necessaryfor a synchronous motor to reach its synchronous speed. Relaysresponsive to the electrical condition of the direct current fieldwinding have been used, but these relays are adjusted so that they willnot respond unless the motor reaches a predetermined speed. If the motoris overloaded, it may still be desirable to force it to operate atsynchronous speed by energizing the direct current field, although theinduction motor torque may not be sufficient to increase the speed to apoint where the pre-set frequency relay responds. By the use of thepresent invention, a long time delay interval may be obtained betweenthe closing of the alternating current contactor and the direct currentcontactor, which time interval is dependent, not upon the attainment ofa predetermined speed. but upon the amount of current flowing in theprimary circuit during that interval regardless of motor speed.

It is, therefore, a further object of the present invention to provide acontrol system suitable for controlling the switching operation of asynchronous motor after a time interval dependent upon the amount ofcurrent flowing in a circuit of the motor regardless of whether or notthe motor has reached a predetermined speed.

Another object is to provide a readily adjustable time delay meanshaving no moving parts, other than the movable contacts of a smallrelay, for controlling the acceleration of a motor in accordance withthe value of current flowing to the motor.

Other objects and advantages will become apparent from the followingspecification, wherein reference is made to the drawings, in which;

Fig. 1 is a simplified wiring diagram illustrating the time delaycircuit and a connection between the circuit and an induction motor;

Fig. 2 is a simplified wiring diagram illustrating the time delaycircuit and another connection between it and an induction motor; and

Fig. 3 is a complete wiring diagram of the control system of Fig. 1.

In the form of our invention illustrated in Fig. 1, three supplyconductors, LI, L2 and L3, connect an electric translating device, shownas an induction motor M, to a source of polyphase power (not shown). Themotor M, as illustrated, is a wound rotor induction motor having theterminals of its rotor winding connected to sliprlngs, which, in turn,may be connected to any type oi secondary impedance controller. Thecontrol circuit includes a transformer 3 having a primary potentialwinding 2 which is connected in series with a resistor 26 across any twoof the conductors LI, L2 and L3, depending upon the positions of theadjustable connectors 21 and 23. The transformer 3 has a primary currentwinding I which is arranged to be connected in series with one or theother of the conductors L2 or L3, depending upon the position of a knifeswitch 8. The transformer 3 supplies alternating current to a full waverectifier 9 through a secondary winding 5. The rectifler 9 may be of anysuitable type but preferably includes a rectifying device 4 and a filtercondenser B. The direct current output of the rectiher 9 is supplied toa stabilizing resistor I. Connected across the resistor I is a timedelay circuit 35.

The time delay circuit 35 depends for its operation upon the timerequired to charge a condenser through a resistor and includes anadjustable resistor H, the contacts 3Ia of a relay 3 I, and a timingcondenser 30 connected in series between the two terminals of the timedelay circult, and an operating winding 3Iw for the relay 3i connectedin series with a discharge device 32, the winding 3Iw and device 32being connected in parallel with the condenser 30. By adjustment of theresistor II, a wide range of selected charging times for the condenser30 may be readily obtained.

The discharge device 32 may be of any suitable type, but preferably hascold electrodes arranged in an attenuated gaseous atmosphere of neon,helium, argon, or the like. The contacts 3Ib of the relay 3|, whenclosed, provide a discharge path for the condenser 30 through theoperating winding 3Iw to completely discharge the condenser 30. Anadjustable resistor 33 may be included in the discharge circuit tolengthen the discharge time and consequently the time during which therelay 3| is energized. Another pair of contacts Me of the relay II isprovided to control the acceleration contactors for th motorM in amanner to be described.

Any transformer connected to a source of constant potential ordinarilyresists any tendency toward flux diminution and tends to make theresultant flux substantially constant. Therefore, any increase in theopposition flux produced by winding I tends to produce more flux in thewinding 2. Assuming no resistor 2! is included, the resultant increasedflux of winding 2 is accompanied by an increase in current in thecircuit which includes the winding 2. However, because the resistor 28is included in the circuit of the winding 2, the increased currentproduced as above described results in a decrease in voltage across thewinding 2, and consequently the flux produced by the winding 2 remainssubstantially constant. As a result, the differential between the fluxesproduced by the two windings varies inversely to the increase of theflux produced by the winding I. If the windings I and 2 are wound sothat the flux set up by the winding 2 is always greater than and opposedby the flux set, up by the winding I, the resulting flux will cause avoltage across the winding -5 which is directly related to thedifferential of the two fluxes, and consequently inversely related tothe amount 01 flux produced by the winding I, to the amount of currentflowing to the motor, and to the load on the motor. If the current ishigh, the opposition flux due to the winding I is greater and thevoltage across the secondary winding 5 is correspondingly reduced. Thelower the voltage across the winding 5, the lower the direct currentvoltage output of the rectifier 3, and the longer the charging time ofthe condenser 30.

Assuming that the windings I and 2 are so wound in relation to thecurrents flowing therein that the fluxes oppose each other, it isobvious that the currents in the two windings must be substantially inphase in order to obtain the desired voltage reduction in the rectifieroutput. The proper phase relationship may be obtained by means of theknife switch 8, which has a pair of blades 8a and separate blades 8b and8c. The blades are preferably arranged to be operated simultaneously asshown in Fig. 3.

When the knife switch Ii is in one position, the blades 8a connect theprimary winding I in series with the conductor L3 and the bladecompletes the circuit from the conductor L2 to the motor M. When theknife switch 8 is in the other position, the blades 8a connect theprimary winding I in series with the conductor L2 and the blade 3bcompletes the circuit from the conductor L3 to the motor M.

By merely properly positioning the knife switch 8, it; is possible toselect a motor current which is within at least 60 degrees of being inphase with the voltage across the conductors to which the potentialwinding is connected. Further phase adjustments can be made by alteringthe connections to the potential winding 2 by means oi. the adjustableconnectors 21 and 2B.

The system, as illustrated in Fig. 2, eliminates the necessity ofobtaining proper phase relationship by the use of two separatetransformers.

In Fig. 2, a current transformer II) has a primary winding II connectedin series with one of the conductors, shown as conductor L3, of thethree supply conductors Ll, L2 and L3 leading from a source of polyphasepower (not shown) to the induction motor M. The transformer II has asecondary winding I2 across which is connected a rectifier I3, includinga full wave rectifying device H, the output terminals of the rectifieri! being connected to a stabilizing resistor i5. Across any two of thesupply conductors, shown as conductors L2 and L3, is connected a primarywinding 2| of a potential transformer 20 having a secondary winding 22.Across the secondary winding 22 is connected a full wave rectifier 23including a rectifying device 2|, the output terminals of the rectifier23 being connected to a stabilizing resistor 25. A filter condenser lilis connected in parallel with the resistor I and a filter condenser 25is connected in parallel with the resistor 25 for smoothing out theoutput voltages of the rectifiers i3 and 23 respectively.

One terminal of each of the resistors i5 and 25 are connected togetherby means of a conductor IS. The other terminal of the resistor 25 isconnected to one terminal of the time delay circuit 35, described inconnection with Fig. 1. Since the time delay circuit is essentially thesame in all the illustrative embodiments, like elements thereof arereferred to by like numerals throughout all figures and descriptions ofthe present specification. The other terminal of the time delay circuit35 is connected to a point on the resistor i5 through an adjustableconnector l9.

It is apparent that any alternating voltage between the conductors L2and L3 is transformed and rectified by means of the transformer 20 andthe rectifier 23 and causes a direct current to flow through theresistor 25. This current causes a potential drop across the resistor 25which charges the condenser 30 through the closed circuit including theresistor l'l, portion n of the resistor i5, and the conductor l6. Aftera definite time delay period, the potential across the condenser 30 willhave reached a magnitude such that the discharge device 32 breaks downand permits current to fiow through the winding 38w of the relay 3|. Therelay 3i, in response to energization of its winding 3Iw, closes itscontacts Me to control the motor, closes its contacts Jib to completelydischarge the condenser 30, and opens its contacts 3m to disconnect thecoil Slw and the condenser 30 from the charging circuit.

The time delay interval obtainable by a circuit using the transformer 20alone is, however, accurately and definitely predetermined in extent. Inorder to change the time delay interval so that it will be longer if themotor is heavily loaded and shorter if the motor is lightly loaded, thecurrent transformer Ill and the rectifier i3 have been provided. Ifcurrent fiows through the primary winding II, a voltage is presentacross the secondary winding l2 and becomes rectified by the full waverectifier l3, causing a direct current to flow through the resistor i5.This current causes a potential drop across the resistor i5 inopposition to the potential drop across the resistor 25, that is, thevoltage across the resistor 25 tends to make the right-hand plate of thecondenser 3|) negative, whereas the voltage across the resistor l5 tendsto make the left-hand plate of the condenser 30 negative. The differencein value between these two potential drops is the resultant voltageeffective for charging the condenser 30. Since the resultant voltage isless than the voltage drop across the resistor 25 alone, a longer timeis required to charge the condenser to any particular value, theadditional time being directly dependent upon the amount of currentflowing to the motor M or the particular translating device beingcontrolled, and, in the case of a motor, therefore, being inverselyrelated to the load.

A current transformer having its primary winding in series with a motorarmature produces a voltage across its secondary winding which isproportional to the current in the armature circuit, provided that thecurrent transformer is designed to maintain its transformation ratioconstant over a necessary range. As is well known, the starting currenttaken by any particular electric motor varies to a great extent. Fromthe characteristics of a current transformer, it is known that thesecondary ampere turns are approximately equal to the primary ampereturns and that the voltage across the secondary is equal to the productof the secondary current and the resistance connected across itsterminals.

The voltage drop across the resistor 25 must always be greater than theopposition voltage drop across the effective portion of the resistor i5so that the resultant voltage charges the condenser at a rate which isin an inverse relation to the motor current, and eventually to a valuesuch that the condenser will discharge through the device 32. If thepotential drops across the two resistors were equal, the condenser wouldnot charge, and if the voltage drop of the resistor l5 were greater thanthe voltage drop of the resistor 25, the condenser would charge at arate directly related to the motor current, and the time of chargingwould be in an inverse relation instead of in a direct relation to themotor current. It is desired to always charge the condenser at a ratewhich is inversely related to the electrical condition of a motorcircuit so that its time of charging is directly related to suchelectrical condition.

In case the motor M should be stalled and thus be taking a high current,it is possible that the voltage across the resistor i5 would be as greatas or greater than the voltage across the resistor 25. To prevent such acondition from occurring, the current transformer i0 is preferablydesigned with an iron core of such a cross section that it can becomesaturated when a current of comparatively low value is flowing throughthe winding ii. Thus, by proper design of the current transformer ill,the motor M can be started and properly accelerated eventually eventhough it is stalled so as not to start on the first few steps ofcontrol, or for other reasons requires excessive starting currents.

Referring now to Fig. 3, the wound rotor induction motor M is arrangedto be energized through the three conductors Ll, L2 and L3, leading froma source of power (not shown). interposed in the conductors LI and L2 isan electromagnetic contactor 40 having an operating winding 40w,interposed in the conductors L2 and L3 is an electromagnetic contactorll having an operating winding liw and normally-open auxiliary contactsMa, and interposed in the conductors L2 and L3 is an electromagneticcontactor 42 having an operating winding 42w and auxiliary contacts420.. The contactor H is arranged to connect the conductors L2 and L3 tothe motor M so that the motor operates in the forward direction, whereasthe contactor 42 is arranged to connect the conductors L2 and L3 to themotor M so that the motor M rotates in the reverse direction.

The secondary winding of the motor M is connected to a suitable currentlimiting device, illustrated as a star-connected resistance bank havingthree branches, RI, R2 and R3. Each of the three resistance branches RI,R2 and R3 comprises four resistance sections, a, b, c and d, connectedin series, electromagnetic contactors 5D to 53 inclusive are associatedwith the resistance bank. The electromagnetic contactor 5|) isoperative, when closed, to short circuit the section a, theelectromagnetic contactor 5| is operative, when closed, to short circuitthe sections a and b, the electromagnetic contactor 52 is operative,when closed, to short circuit the sections a, b and c, and theelectromagnetic contactor 53 is operafive, when closed, to short circuitthe sections a, b, c and d. Operating windings 50w, 5lw, 52w and 53w areassociated with the contactors 50 to 53 inclusive, respectively. Thecontactors 5| and 52 have normally-open auxiliary contacts 5 lb and 521)respectively and normally-closed auxiliary contacts 5|a and 52arespectively. The contactor 50 has a normally-open auxiliary contact50a.

The resistance section a of the resistors RI R2 and R3 is the pluggingsection, and its associated short circuiting contactor 50 is under thecontrol of a relay 8| having a winding Blw connected in series with acondenser 60 across the resistance section a. This type of pluggingrelay is more fully described in the co-pending application of John D.Leitch which resulted in Patent No. 2,165,491 on July 11, 1939.

Electromagnetic relays 54, 55 and 56 are provided to control theoperation of the contactors 5|, 52 and 53 respectively and haveoperating windings 54w. 55w and 56w respectively. Each of the relays 54,55 and 56 has two normally-open contacts denoted by the correspondingnumerals with subscripts a and b respectively and one normally-closedcontact denoted by thacorresponding numerals with the subscript c.

The operation of the relays 54, 55 and 56 is automatically controlled bythe relay 3|, the winding 3|w of which is connected in parallel with thecondenser 30 of the timing circuit 35, which is the same timing circuitas the timing circuit designated in Figs. 1 and 2 by the numeral 35.

In Fig. 3 the timing circuit 35 has been shown as connected to theconductors leading to the motor M in the manner disclosed in Fig. 1, itbeing understood that the connections of Fig. 2 could be used as well.

The primary winding I of the transformer 3 is arranged to be connectedin series with either one of the conductors L2 or L3, depending upon theposition of the knife switch 8. When in the lower closed position, theblades 8a of the knife switch 6 connect the winding l in series with theconductor L3 and the blade 80 completes the circuit for the conductorL2. When in the upper closed position the blades Ba connect the windingI in series with the conductor L2 and the circuit to conductor L3 iscompleted through the blade 81).

For clearness in illustration, the connectors 21 and 28, shown in Fig.l, have been omitted from Fig. 3, since their use is not essential tothe operation and, if desired, they could be interposed in theconductors 9|) and 93 in a manner which is disclosed in Fig. 1.

To control manually the direction of rotation h and speed of the motorM, a master switch 60 is provided. The master switch 60 includessegments G2 to 61 inclusive for controlling the acceleration in theforward direction, and segments 12 to 11 inclusive for controlling theacceleration in the reverse direction. A segment BI is arranged forselectively connecting the various segments 62 to 61 inclusive and 12 to11 inclusive to the source of power. The circuit terminals 1| arerelatively movable to any of the forward or reverse positions tocomplete various circuits from the source of power to the relays andcontactors.

The operation of the controller diagrammatically shown in Fig. 3 is asfollows:

Assume that power is supplied to the conductors Ll, L2, and L3, that theknife switch 8 is in a closed position, and that the master switch 6|]is moved quickly from the ofi position to any position in the forwarddirection. In such case, the circuits to the operating windings of thecontactors 46 and 4| are completed without any time delay. The circuitto the winding 4010 is from the conductor L3 through a conductor 90, oneoi! the circuit terminals H the segment 6| oi the master switch 60, thesegment 62, another of the circuit terminals H, a conductor 9|, thewinding 40w, and the conductors 92 and 93 to the conductor L2. Thecircuit to the winding 4 lw is completed from the energized segment 6|to the segment 63, a conductor 94, the winding M11), and the conductors95 and 93 to the conductor L2.

The contactors 4|) and 4| close their main contacts in response to theenergization of their operating windings to connect the primary windingof the motor M to the source of power. Immediately upon the closure ofthe contactor 4|, the contactor 50 closes to short circuit the pluggingresistance section a of the resistor banks RI, R2 and R3. The circuit tothe operating winding 50w of the contactor 50 is from the energizedsegment 6| to the segment 64, through a conductor 96, the now closedauxiliary contacts 4|a of the contactor 4|, a conductor 91, thenormallyclosed contacts Bla of the plugging relay 8|, the winding 50w,and conductors 99 and 33 to the conductor L2. The contacts of theplugging relay Bl are not opened at this time because the resonantcircuit including the winding 8|w and the condenser is adapted to causeenergization of'the relay 8| only when a current of substantially twiceline frequency flows in the secondary winding of the motor M.

The closure oi! the contactor 4| also completes a circuit to the primarypotential winding 2 01 the transformer 3 which is from the energizedconductor 91 through a conductor I01, the normally closed contacts 54cof the relay 54, a conductor llll, the primary winding 2, the resistor26, and the conductor 93 to the conductor L2.

Assuming that the position to which the master switch was movedinitially was to the fourth position in the forward direction, aparallel circuit is completed to the primary potential winding 2 of thetransformer 3. This circuit is from the energized segment 6| to thesegment 65, through conductors I00 and 44, the normallyclosed contacts550 of the relay 55, the conductors I02 and IN, the primary winding 2,the resistor 26 and the conductor 33 to the conductor L2. In this fourthposition of the master switch, a further parallel circuit is completedlikewise to the primary winding 2 through the segment 66, a conductorIII), the normally-closed contacts 560 of the relay 56 and the conductor13 to the conductor |0| and thence through the winding 2, the resistor26, and the conductor 93 to the conductor L2.

The primary series winding I of the transformer 3 is energized by virtueof its being connected in series with the conductor L3 or L2, de-

pending upon the position of the knife switch 3. with both the primarywindings I and 2 energized, the timing circuit 33 is ready i'oroperation. The circuit to the condenser 39 is completed through the nowclosed contacts 39:: of the plugging contactor III and the conductors33. Consequently, the condenser 39 begins to charge, and continues to doso by virtue of a voltage created by the differential in the opposedfluxes set up by the currents in the winding I and 2, as more fullydescribed in connection with Fig. 1. Therefore, the condenser charges ina time interval which depends upon the adjustment of the resistor I1 andwhich is directly related to the amount of current flowing in theconductors L2 or L3. The higher the motor current, the slower thecharging rate, and the longer the charging time. The condenser istherefore charged at a rate inversely in accordance with the electricalcondition of a motor circuit.

The condenser 39 continues to charge until it is charged to apredetermined potential, upon the attainment of which the condenserdischarges through the winding 3Iw and the device 32. The relay 3|operates in response to the energization of its operating winding 3Iwand closes its contacts 3Ic. The closure of the contacts 3Ic sets up acircuit extending from the energized conductor 99. through a conductorI, the contacts 3Ic, a conductor I95, the normally-closed contacts Bioof the acceleration contactor II, a conductor I99, the winding 94w therelay 94, and the conductors 99 and 93 to the conductor L2. In responseto the energization of its operating winding 53w, the relay 53 closesits contacts a and 59b and opens its contacts 540.

The movement of the relay 3I to the energized position also causesclosure of contacts 3 lb which permits the complete discharge oi thecondenser 30 through a circuit such as illustrated and which includesthe resistor 33 and the winding 3Iw. The time of discharge. andconsequently the time during which the relay 3| is energized, may bepredetermined by adjustment of the resistor 33. As soon as the condenser39 is completely discharged, the relay winding 3Iw is deenergized andthe relay 3| returns to its normal position. The relay 54 remainsenergized to maintain the circuit to the winding Blw of the contactor5|, however, since the contacts Ila, when closed, complete a holdingcircuit for the winding 54w, which circuit extends from the nowenergized conductor 91 through the conductor II", the contacts 53a, thewinding w, and the conductors 99 and 93 to the conductor L2. The closureof the contacts 53b completes a circuit from the now energized conductorI 99, through the contacts 54b, a conductor I99, the operating winding9lw of the contactor BI, and the conductors 99 and 93 to the conductorL2.

The contactor Si in response to energization of its operating windingBlw closes its main contacts to short circuit the resistance sections aand b causing an increase in torque of the motor M or a change in theoperation of the particular translating device under control. If themotor M is free to rotate, the short circulting of the resistancesections a and b results in an increase in speed. Opening .of thenormally-closed contacts 540 disconnects one circuit to the transformerwinding 2 but the winding 2 remains energized through thenormally-closed contacts 950 and Site. If the master switch 99 had beenmoved only to the first position, the circuits through thenormally-closed contacts 550 and 580 would not be completed through thesegments 93 and 99 of the master switch 99, and further shunting of theresistance sections would be arrested.

By adjustment of the resistor 33 or by proper selection of theresistance of the winding 3Iw. the contacts 3 le are caused to Openduring the interval between the closing of the contacts 54a of the relay54 and the contacts 3 lb of the contactor II. Upon deenergization of therelay 3 I, the contacts 3Ia close to start the second time interval, andits duration is determined by the potential applied to the condenser 39,this potential being derived from the opposed fluxes as in the precedingstep above described. At the expiration of the second time interval, therelay 3I again operates and this time causes energization of the winding3510 of the relay 93.

The circuit to the winding 55w is from the energized conductor I99,through the contacts Me, the conductor I99, the normally-closed contacts92a 01 the contactor 52, the now closed contacts lb of the contactor il,a conductor I99, the winding 55w, and the conductors 99 and 93 to theconductor L2. The closure of the contacts "a in response to theenergization of the winding 33w completes a holding circuit for thewinding to so that its energization is not dependent upon the subsequentdeenergization of the relay 3|. This holding circuit extends from theenergized conductor I99 through the conductor II. the contacts 53a, thewinding 55w, and the conductors 99 and 93 to the conductor L2. Closureof the contacts 551: completes a circuit from the energized segment 9|,through the segment 69, the conductor II9, the contacts 55b, a conductorIII, the winding 5210 of the contactor 92. and the conductors 99 and 93to the conductor L2. The contactor 52 in response to energization of itsoperating winding 92w closes its main contacts to short circuit theresistance sections a, b and c to permit a further increase in motortorque.

Opening of the normally closed contacts We of the relay 55 disconnectsone of the remaining parallel circuits to the primary winding 2, but theprimary winding 2 remains energized through the normally closed contacts580. since the master switch 69 is in the fourth position. Shortly afterthe contacts 55a. close and shortly before the contacts 52b close, therelay 3| returns to its normal position and starts another timinginterval.

At the expiration of this new timing interval, the relay 3| again closesthe contacts 3lc, which this time complete a circuit from the conductorI99 to the conductor I95, the now closed contacts 52b of the contactor52, a conductor "2, the winding 5910 of the relay 55, and the conductors99 and 93 to the conductor L2. In response to energization of theoperating winding 58w, the relay 53 closes its contacts 56a to completea holding circuit for the winding 56w and also closes its contacts 96bto complete a circuit from the energized segment GI through the segment91, a conductor I I3, the now closed contacts 5612, a conductor H4. thewinding 53w of the contactor 53, and the conductors 99 and 93 to theconductor L2. The holding circuit for the winding 59w is from theenergized conductor IIIl through the contacts 530, the winding 58w, andthe conductors 99 and 93 to the conductor L2.

The contactor 53 in response to energization of its operating winding53w closesits contacts to short circuit all of the resistance sectionsa, b, c and d to permit the motor M to operate at its normal speed or toexert its normal torque. The

primary winding 2 is now disconnected from the source because thecontacts 54c. 55c and lie are opened, and consequently the timingcircuit no longer operates. Thereafter, ii the current in the winding tshould be enough to cause charging of the condenser 30 to its dischargevalue, no circuits would be changed upon operation of the relay 3|.

If it is now desired to stop or reverse the motor M, the master switch60 may be moved from the fourth position in the forward direction to anyposition in the reverse direction. All of the contactors and relaysbecome deenergized as the master switch 60 is moved through the offposition, but the contactors l and 4! become energized to supply reversepower to the motor I! as soon as the master switch Bil is moved to oneof the reverse positions. At the instant that reverse power is applied.the frequency of the current flowing in the resistance section a of theresistance branch RI becomes approximately equal to twice the frequencyof the source oi. supply. As a result, the tuned circuit including thecondenser 80 and the operating winding 8Iw of the plugging relay 8|becomes energized and causes opening of the contacts Mo to prevent theenergization of the operating winding 50w of the contactor 50. Thecontactor 50 is thus held in open position to prevent the starting ofthe timing period for the acceleration contactors 5|, 52 and 53 and alsoto prevent the short circuitin of the resistance section a during thetime that the motor is decelerating from a forward running condition toa stand-still condition. As the motor speed approaches zero, thefrequency of the current in the resistance section 11 decreases to thefrequency of the source of supply. At this time, the relay winding 8 I10becomes deenergized and permits the reclosure of the contacts 8 la.

As soon as the contacts Ola are closed, the winding 50w becomesenergized over a circuit previously described in connection with theforward direction of operation except that the contacts 42a instead ofthe contacts Ma complete the circuit. The contactor 50 consequentlycloses to short circuit the section a and also closes its auxiliarycontacts 50a which starts the timing peirod for the contactor 5|. If theposition to which the master switch 60 is moved is the fourth positionin reverse, the resistance sections b, c and d are caused to becomeshort circuited successively, each in delayed relation to itspredecessor, by means of the contactors 5|, 52 and 53. the relays 54, 55and 5G, and the timing circuit 35, as previously described in connectionwith the forward direction of rotation.

It will be obvious to those skilled in the art that if the master switchis moved from the off position to the first, second or third positionsin the forward or reverse directions, a similar sequence of operationswill take place depending upon the position in which the master switch60 is placed, except that certain of the accelerating contactors beyondsaid positions in the direction of movement of the switch 60 will notclose. For instance, in the first position only contactor 50 will close,in the second position 50 and ii will close successively in delayedrelation, and in the third position 50, 5| and 52 will closecorrespondingly, so that the delayed intervals are cumulative for anyselected on position.

If at any time when the motor M is running, it is desired to control itsspeed, the master switch ill may be moved to any selected position andleft there. If the speed is to be increased by such movement, the properamount of secondary resistance will be short circuited after time delayintervals. It the speed is to be reduced by such movement, the properamount of secondary resistance will be reinserted by operation of someor all of the contactors B0 to 53 inclusive. depending upon the extentof movement oi the master switch M. r

The system of interlocking contacts shown in Fig. 3 is applicable onlywhen the relay lilre-, mains closed for but a short interval of time.This short interval may be obtained by so designing the coil liw that ithas a very small ohmic resistance, since the discharge time of acondenser is directly dependent upon the ohmic resistance of itsdischarge path. The resistor 33 shown in Fig. 1 may be used to give anadjust ment of the discharge time. The relay 3| need only be energizedlong enough to cause closure of the proper one of the relays 54, 55 or56, and must become deenergized and open the contacts 3lc before eithercontactor 5| or 52 closes its respective auxiliary contacts Slb or 52b.

Although the relay system shown for purposes of illustration has certainadvantages peculiar to itself, it will be obvious to those skilled inthe art that relay systems other than the one disclosed and having someof the advantages thereof, or other advantages, can be devised readilyafter having the benefit of the applicants description. For instance, incontrollers employing contactors which close very rapidly, additionalrelays can be used to prevent the operation of more than one contactorfor a single operation of the timing relay 3 I. In such case, thecontactor and relay operation can be made independent of the length oftime that the relay 3| is energized.

The invention is not limited to the control of secondary resistanceshunting switches, since the same fundamental circuit can be readilyadapted to control the shunting of primary impedance, the operation ofan electromagnetic compensator for controlling the voltage applied tothe primary of an induction or synchronous motor, the application of thedirect current field in the case of a synchronous motor, and switchingoperations of any other electrical translating device.

We claim:

1. In a control system for an electrical translating device including acircuit and employing the charging of a condenser for controlling theoperations of the device, means for charging the condenser at a ratewhich is inverse to an electrical condition of the circuit of the deviceto be controlled and comprising a coil operatively connected to thecircuit of the device for energization in a direct relation to thedegree oi energization of said circuit, another coil connected to adifferent source of energy and operative to produce flux in oppositionto and greater in intensity than the flux produced by the first coil, acoil connected to the condenser and oprative, when it is energized, tocause charging of the condenser, and all of said coils beingconcurrently inductively related to each other, whereby the condenser isenergized by flux resulting from the difierential in the flux of the twofirst mentioned coils.

2. The combination with an electric translating device to be controlled,a control system operable when energized for controlling the device, acondenser operative when charged to a predetermined value to dischargeautomatically, means responsive to the discharge current of thecondenser for effecting energization of the con- I prising acceleratingmeans for the motor, means to arrest for temporary periods theaccelerating action of the accelerating means in difierent stagesthereof, the arresting means including a control circuit adapted to beelectrically associated with a motor circuit for energization thereby, acondenser, charging means for the condenser and connected to thecondenser and to said control circuit in a manner to cause said chargingmeans to charge the condenser at a rate inversely related to the amountof current flowing to said motor when the control circuit iselectrically associated with said motor circuit, and means responsive toa predetermined charge on said condenser for operating said acceleratlngmeans.

4. The combination with an electric translating device to be controlledand including a circuit having a variable electrical condition dependentupon the operating condition of the device, a control system operablewhen energized for controlling the device. a condenser operativelyassociated with the control system and operative when charged to apredetermined value to discharge automatically, and means operated bythe discharge from the condenser for efiecting energization of thecontrol system, of a condenser charging circuit electrically associatingthe condenser and the circuit of the device in a manner to cause thecondenser to charge at a rate which is dependent upon and in inverserelation to the electrical condition of said circuit of the device.

5. A control system for controlling the control means of the knowncombination of an electric circuit and a control means for the electriccircuit, said control means comprising a current responsive deviceadapted to be energized when connected to said circuit and when soconnected and energized operative by current flowing in said circuit 'toproduce an electrical condition directly related to said current, adevice capable of producing a substantially constant electricalcondition similar to and continuously predominant in magnitude withrespect to and in substan-tial alignment vectorially with the electricalcondition produced by the current responsive device, means operativelyassociated with the said devices to operatively associate saidelectrical conditions to render the arithmetical 'difi'erential in saidconditions available for operation of the control means, and meansassociated with the control means and said last named means and, when soassociated, responsive only to the magnitude of said differential inconditions to control said control means in accordance with themagnitude of said differential in said electrical conditions.

6. A control system for controlling the control means of the knowncombination of an electric translating device having a circuit and acontrol means for the electric translating device, said control systemcomprising a current responsive device adapted to be 'energized whenconnected to said circuit to produce a unidirectional voltage in directrelation to the current in said circuit, a device capable of producing asubstantially constant unidirectional voltage continuously predominantwith respect to the voltage produced by the current responsive device,and circuit means electrically connected to the control means andoperatively associated with said devices and having impressed thereonthe said two voltages for relating the said two voltages to create adiiferential in said voltages available i or controlling the controlmeans.

'7. A control system for controlling a control means in response to theelectrical condition of an electric circuit of an electrical translatingdevice controlled by said control means, said system comprising meanselectrically associated with said circuit for creating an alternatingflux directly related to the electrical condition of said circuit, andmeans for creating an alternating flux which is continuously greaterthan the alternating flux created by said first flux creating means,means associated with the said two flux creating means for relating thesaid two fluxes to create a differential alternating flux, and meansresponsive to said differential flux to control said control means inaccordance with the amount of said diiferential flux.

8. A control system for controlling the control means or the knowncombination of an electric circuit and a control means for the circuit,said control system comprising means for creating an alternating currentflux directly related to the amount of current flowing in said circuit,means for creating an alternating flux which is continuously greaterthan the alternating flux created by said first flux creating means,means associated with the said two flux creating means for relating thetwo fluxes to create a differential alternating flux, means responsiveto said differential flux for creating a voltage directly related tosaid diiferential flux, and time delay means associated with saidcontrol means and responsive to said voltage for controlling saidcontrol means after an interval of time indirectly related to the amountof said diiierential flux.

9. A control system for controlling the control means of the knowncombination of an electric circuit and a control means for the electriccircuit, said system comprising a current responsive device adapted forconnection to said circuit and when so connected operative by thecurrent flowing in said circuit to produce an electrical conditiondirectly related in magnitude to said current, a device capable oiproducing a substantially constant electrical condition similar to andcontinuously predominant with respect to the electrical conditionprovided by the current responsive device, means operatively associatedwith the said devices to associate said electrical conditions to createa differential in electrical conditions, an energy accumulator which isoperatively associated with the first named means and is renderedoperative by said diflerentlal in electrical conditions, and meansoperatively associated with the control means and operated by theaccumulator for causing operation of said control means, whereby thecircuit is controlled in an inverse relation to the current flowingtherein.

10. A control system for controlling the control means of the knowncombination of an electric translating device which is adapted forconnection to a main circuit and a control means therefor, said systemcomprising a current responsive device adapted for connection to saidmain circult and when so connected operative by current flowing in themain circuit to create an electrical condition in direct relation tosaid current, a device for creating an electrical condition in relationto the electrical condition of the first device sufllclent to provide adifierential electrical condition which is in inverse relation to thecurrent flowing in the main circuit, a time delay means operativelyassociated with said devices and with said control means and including acondenser and means operated. thereby when said condenser is charged toa predetermined degree to operate said control means, and meansoperatively associating the condenser with the diflerential electricalconditlon to charge the condenser in accordance with said differentialelectrical condition.

11. A control system for controlling the operation of the control meansof the known combination of an electric translating device which isadapted for connection to a main circuit and a control means therefor,said system. comprising a current responsive device adapted forconnection to said main circuit and, when so connected, operative bycurrent flowing in the main circuit to produce a variable voltage indirect relation to said current, means for supplying another voltagedifferent from the variable voltage, and means to relate said voltagesin a manner to produce a dlfierentlal voltage which is in inverserelation to the current flowing in the main circuit, and a condenserconnected to said devices in a manner to be charged by said diiierentialvoltage and operatively associated with said control means and operativewhen charged to a predetermined degree to discharge and to effectoperation of said control means.

12. The combination with an electric motor, an energy absorbing devicecapable of being charged to a predetermined potential, and meansresponsive to a predetermined potential across said device for changingthe condition of motor operation, of means adapted to be connected to acircuit of the motor and when so connected capable of creating a voltageequal to the differential between a voltage proportional to the currentin the said motor circuit and a substantially constant continuouslypredominant reference voltage, and means for subjecting said energyabsorbing device to said differential voltage to produce saidpredetermined potential, whereby said motor operation is controlled ininverse relation to the current in the motor circuit.

13. The combination with a motor acceleration system wherein a chargeabsorbing device operates as an arresting means to arrest the action ofan acceleration means until the accumulation of a predetermined chargeon the device, of a charging means having an output voltage inverselyrelated to the value of current flowing in said motor circuit andoperative to charge said charge absorbing device.

14. The combination with an accelerating means for an electric motor,means to arrest for temporary periods the accelerating action of theaccelerating means in different stages thereof, the arresting meansincluding a control circuit adapted to be electrically associated with amotor circuit, an energy absorbing device in said control circuit, andmeans responsive to' a predetermined electrical cause operation oitricai translating device adapted to be connected for operation to asource of power through a supply circuit and a control means for theelectrical translating device, said control system comprising a controlcircuit electrically associated with said supply circuit for producing avoltage proportional to the current in said supply circuit when saiddevice is connected for operation, a control circuit for producing avoltage similar to and continuously predominant over that produced bythe flrst control circuit, means adapted to electrically associate saidcircuits to cause said voltages to be in opposed relation to each other,an electrical charge absorbing device, said charge absorbing device andsaid control circuits being electrically connected together in a mannerto subject the charge absorbing device to the difl'erential in saidopposed voltages for charging said charge absorbing device, and meansadapted to control the control means in response to a predeterminedcharge on said charge absorbing device.

16. The combination with an electric translating device to becontrolled, a control system operable when energized for controlling thedevice, a. condenser, means responsive to a predetermined electricalcondition 01 the condenser for effecting energization of the controlsystem, and means operable for electrically associating the condenserwith a voltage dependent upon the amount of current flowing to saiddevice for charging the condenser by said voltage, of means forrendering the last named means operative in inverse relation to the saidamount of current.

1'1. The combination with an alternating current motor, adapted to beconnected to a source of alternating current through supply conductors,a control system operable when energized for controlling the motor, acondenser, and means responsive to a predetermined electrical conditionof the condenser for effecting energization of the control system, ofmeans inductively related to said supply conductors for charging thecondenser wlth a voltage inversely dependent upon the amount of currentflowing to said motor through said conductors.

18. The combination recited in claim 13 characterized further in thatthe charging means comprises a transformer, a rectifier for producing aunidirectional voltage proportional to the secondary voltage of thetransformer, a source of unidirectional voltage, and a circuit foropposing the two unidirectional Voltages to obtain said output voltage.

WILLIAM J. KUTCHER. JOHN D. LEITCH.

CERTIFICATE OF CORRECTION. Patent 'ue. 3,2!!!7506. July 1, 19m.

' WILLIAM J. KUTCHER, ET AL. It is hereby certified that error appearsin the printed specification of the above numbered patent requiring a)rrection as follows: Page 7, first column, line ha, for "paired" read--period--; page 8, first column, iine 11.5, claim 5, for the word"means" read --syetem; and that the said Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent Office.

si ned and sealed this 16th day or September, A. 1). 191m.

Henry Van Aredale,

(Seal) Acting Commissioner of Patents.

